Magnetic head for perpendicular recording with magnetic loop providing non-perpendicular write field

ABSTRACT

A magnetic head for writing information on perpendicular media has a write pole tip and a return pole tip with a media-facing area at least two orders of magnitude greater than that of the write pole tip, the return pole tip is spaced from a trailing corner of the write pole tip by a submicron nonferromagnetic gap. Magnetic flux emanating from the write pole tip is strongest adjacent the trailing corner and directed at an angle that is not perpendicular to the write pole tip. The angled flux provides increased torque to rotate magnetic dipoles in the adjacent media layer that are oriented substantially perpendicular to the disk surface. The media may have a soft magnetic underlayer that is spaced from the write pole tip by a distance similar to the gap spacing.

CROSS-REFERENCE TO RELATED APPLICATIONS

Related disclosure of an electromagnetic head for writing information ona relatively-moving medium can be found in the U.S. patent applicationSer. No. 10/724,385, entitled Magnetic Head for Perpendicular Recordingwith Magnetic Structure Providing Non-Perpendicular Write Field, by thesame inventors and filed on Nov. 26, 2003, and assigned to the assigneeof the present application, which is incorporated by reference herein.

BACKGROUND

The present invention relates to electromagnetic transducers forinformation storage and retrieval systems, such as disk or tape drives.

Current commercially available disk drives employ magnetoresistive (MR)sensors for reading data, and store data in domains havingmagnetizations that are substantially parallel to concentric mediatracks, the parallel magnetic storage sometimes called longitudinalrecording. It has been predicted that such longitudinal magnetic storagewill become unstable at normal operating conditions when the domainsreach a minimal size, termed the superparamagnetic limit. In order tostore the data at higher density, the drive system may instead bedesigned to store data in domains that are substantially perpendicularto the disk surface, which may be termed perpendicular recording.

FIG. 9 shows a prior art system for perpendicular recording, whichincludes an inductive transducer 20 positioned in close proximity to asurface 25 of a medium such as a disk 22. The inductive transducer 20has a U-shaped core 30 formed of high-permeability, low-coercivity or“soft magnetic” material and the disk 22 has a soft magnetic underlayer33, the core and underlayer forming a magnetic circuit indicated by fluxlines 28 that traverse a higher coercivity media layer 32, formagnetizing the media layer or reading the magnetization of the medialayer. The core has magnetic pole tips 36 and 38 that differ inmedia-facing area so that the magnetic signal is concentrated in thesmaller pole tip for reading or writing data. The local portion of thedisk may be traveling in the direction of arrow 40 or in a reversedirection, to write magnetic signals on a track. The pole tips aresufficiently separated to encourage magnetic flux to travel through themedia, instead of across a submicron nonmagnetic gap that is typicallyemployed for longitudinal recording. The prior art transducer of FIG. 9is sometimes called a probe head.

U.S. Pat. No. 6,320,725 to Payne et al. discloses a transducer with aring-shaped core terminating in a pair of pole tips that are separatedby a nonmagnetic gap, with write fields emanating from corners of thepole tips closest to the gap, which may be termed a ring head. The ringhead of Payne et al. has a head to medium spacing that is a fraction ofthe gap spacing, so that perpendicular rather than longitudinal writefields predominate in the media layer, with the leading corner of thetrailing pole tip leaving the magnetic signal on the disk.

U.S. Pat. No. Re. 33,949 to Mallary et al. discloses a head forperpendicular recording with a write pole that is shielded with adownstream shield so that non-perpendicular fringe fields do notdemagnetize the perpendicular signal written by the write pole. Mallaryet al. note that reducing the spacing between the head and the mediumallows the spacing between the write pole and the shield to beincreased, because there is a greater incentive for flux to pass betweenthe more closely spaced head and medium.

SUMMARY

In one embodiment, a magnetic head for writing information on arelatively-moving medium is disclosed, the head comprising a body havinga leading end, a trailing end and a medium-facing surface, the bodyincluding an electrically conductive coil section at least partlyencircled by a magnetic loop terminating in a write pole tip and areturn pole tip that are disposed adjacent to the medium-facing surfaceand separated from each other by a nanoscale nonferromagnetic gap,wherein the return pole tip is disposed between the write pole tip andthe trailing end and the return pole tip has a medium-facing area thatis at least two orders of magnitude greater than that of the write poletip.

The head is designed so that magnetic flux emanating from the write poletip is strongest adjacent its trailing corner and directed at an anglethat is not perpendicular to the write pole tip. The angled fluxprovides increased torque to rotate magnetic dipoles in the adjacentmedia layer that are oriented substantially perpendicular to the disksurface. To encourage this angled flux, the medium can have a softmagnetic underlayer that is spaced from the write pole tip by a similardistance as the gap spacing between the pole tips.

In one embodiment, the coil section is part of an electricallyconductive coil that spirals around a first magnetic section thatmagnetically couples the write pole tip to the return pole tip, and asecond electrically conductive coil or winding spirals exterior to themagnetic loop, such that a current spiraling in a first direction in thecoil spirals in a substantially opposite direction in the winding.

In one embodiment, a magnetoresistive sensor can be disposed in the bodybetween a pair of shields that are disposed adjacent to the magneticloop. In another embodiment, the return pole tip can be the terminationof a return pole layer that also serves as a shield for amagnetoresistive sensor.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a cutaway cross-sectional view of an electromagnetic head inproximity to a relatively moving medium.

FIG. 2 is an expanded cross-sectional view of the head of FIG. 1 thatfocuses on a region around the pole tips of that head.

FIG. 3 is an expanded cross-sectional view of the head of FIG. 1 thatfocuses on a region around the pole tips of that head and includes arepresentation of magnetic flux that may be provided by the head duringoperation.

FIG. 4 is a cutaway view of the head of FIG. 1 as seen from the medium.

FIG. 5 is a view of the head of FIG. 1 as would be seen looking at thetrailing end and focusing on the active elements of the writetransducer.

FIG. 6 is a cutaway cross-sectional view of an electromagnetic head inwhich a write transducer is disposed closer than a MR sensor to a wafersubstrate.

FIG. 7 is a cutaway view of the head of FIG. 6 as seen from the medium.

FIG. 8 is a perspective view of dual spiral coil layers interconnectedat interconnect to illustrate one kind of double reverse coil formationthat may be employed.

FIG. 9 is a cross-section of a prior art system for perpendicularrecording, including a transducer with a write pole and a return poleand a medium with a soft magnetic underlayer.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG. 1 is a cutaway cross-sectional view of a magnetic head 60 inproximity to a relatively moving medium 50. The medium 50 includes asubstrate 52 over which a soft magnetic underlayer 55 has been formed. Amedia layer 58 is disposed over the underlayer 55, the media layerhaving an easy axis of magnetization that is substantially perpendicularto a major surface 53 of the medium. A thin, physically hard overcoat 56separates the media layer 58 from the medium surface 53. The medium 50,which may for example be a rigid disk, is moving relative to the head ina direction shown by arrow 59. The head 60 may be spaced from the medium50 by a nanoscale air bearing, or the head may be in frequent orcontinuous contact with the medium during operation. The word nanoscaleas used herein is meant to represent a size that is most convenientlydescribed in terms of nanometers, e.g., between about one nanometer andabout two hundred nanometers.

The head 60 has a leading end 62, a trailing end 64 and a medium-facingsurface 66. A first ferromagnetic layer 68 disposed in the headterminates adjacent to the medium-facing surface in a first pole tip 70.A second ferromagnetic layer 78 is magnetically coupled to the firstferromagnetic layer 68 in a region 65 that is removed from themedium-facing surface 66, the second ferromagnetic layer terminatingadjacent to the medium-facing surface in a second pole tip 80. Thesecond pole tip 80 is disposed between the first pole tip 70 and thetrailing end 64, the second pole tip being separated from the first poletip by a nanoscale nonferromagnetic gap 77.

A third ferromagnetic layer 88 adjoins the first ferromagnetic layer 68but terminates further from the medium-facing surface 66 than the firstpole tip 70, layers 68 and 88 combining to form a write pole layer. Aferromagnetic pedestal 75 and a ferromagnetic stud 79 can be consideredto form part of the second ferromagnetic layer 78. The ferromagneticlayers 68, 78 and 88 of the head 60 may have a permeability of at leastone thousand, while layer 68 may also be formed of a high magneticmoment material, e.g., having a magnetic saturation of at least twentykiloGauss. First ferromagnetic layer 68 has a trailing edge 96 disposedadjacent to trailing end 64. A trailing corner 71 of first pole tip 70,disposed where first pole tip 70 meets trailing edge 96, isapproximately equidistant from soft magnetic underlayer 55 and softmagnetic pole layer 78 in this example. The first pole tip 70, includingthe trailing corner 71, is in this embodiment made of higher magneticsaturation material than that of soft magnetic pole layer 78.

A plurality of electrically conductive coil sections 82 are disposedbetween the first ferromagnetic layer 68 and the second ferromagneticlayer 78 to induce magnetic flux in the first, second and thirdferromagnetic layers 68, 78 and 88. Those ferromagnetic layers 68, 78and 88 form a magnetic loop around coil sections 82, the loopinterrupted by nanoscale nonferromagnetic gap 77. Another plurality ofelectrically conductive coil sections 86 may be similarly disposedbetween the first ferromagnetic layer 68 and the leading end 62. Crosses85 in the coil sections 82 indicate electric current that is flowingaway from the viewer and into the page, while dots 86 in the coilsections 84 indicate electric current that is flowing toward the viewerand out of the page. With electric current flowing in substantiallyopposite directions in sections 82 and 84 as shown, the magnetic fieldfrom the coil sections 82 and 84 adds together in the area between thesections 82 and 84 and is at least partly cancelled in areas outside thesections 82 and 84 that are closer to the leading or trailing end.

The coil sections 82 in this embodiment are part of a first coil layer91 that spirals around stud 79 and coupling region 65 and includeselectrically conductive coil sections 95. Coil sections 84 are part of asecond coil layer 93 that spirals around an axis substantially alignedwith that of the first coil layer, and includes electrically conductivecoil sections 99. Another magnetic stud, not shown, may optionally beprovided at the axis of coil layer 93 and coupled to ferromagnetic layer88. Coil sections 95 have electric current that is flowing toward theviewer and out of the page, as indicated by dots 86, while coil sections99 have electric current that is flowing away from the viewer and intoof the page, as indicated by crosses 85. Advantages of a reversed doublecoil layer configuration such as this include a stronger applied fieldbetween the coil layers 91 and 93 and reduced or cancelled field leadingand trailing the coil layers, as well as reduced coil inductance andreduced amplification of stray signals due to an antenna effect. Thecoil layers may spiral in identical directions, e.g., both spiralinginward in a counterclockwise direction when viewed from the trailingend, and be interconnected at the center sections or outermost sections.Alternatively, the coil layers may spiral in opposite directions andhave the center section of one layer connected to the outermost sectionof the other layer. In one embodiment twelve or fewer coil sections aredisposed between ferromagnetic layers 68 and 89.

Instead of the configuration shown in FIG. 1, coil sections 82 and 84may spiral in a barber pole formation around ferromagnetic layers 68 and88, without the need for coil sections 95 and 99. Alternatively, insteadof plural coil sections 82, a single coil section or multiple coilsections may pass between layers 68 and 78. For the case in which coilsection 82 is a single section formed as a layer, that layer may beconnected to a similar layer disposed between layer 88 and the leadingend 62. This formation may be termed a single turn coil.

The ferromagnetic layers 68 and 78 of the head 60 together with the softmagnetic underlayer 55 of the disk 50 form a magnetic circuit thattraverses the media layer adjacent to the first pole tip 70 and thesecond pole tip 80. Although not clear in this cross-sectional view, thesecond pole tip 80 has a medium-facing area that is at least two ordersof magnitude greater than that of the first pole tip 70, to avoidoverwriting with the second pole tip signals that were imparted to themedia layer by the first pole tip. Ferromagnetic layers 68 and 78 alsoform a magnetic circuit that is interrupted by the gap 77 so that fringefields from that circuit traverse the media layer adjacent to the gap77. These magnetic circuits add to create a maximum magnetic flux in themedia-layer 58 at a location closest to the gap and at an angle fromperpendicular to the medium surface 53.

The head 60 also includes a magnetoresistive (MR) sensor 90 sandwichedbetween first and second soft magnetic shield layers 92 and 94. The MRsensor 90 can be any sensor that utilizes a change in resistance causedby a change in magnetic field to sense that field, which may be measuredas a change in current or voltage across the sensor, includinganisotropic magnetoresistive (AMR) sensors, spin-valve (SV) sensors,spin-tunneling (ST) sensors, giant magnetoresistive (GMR) sensors andcolossal magnetoresistive (CMR) sensors. Other electromagnetic sensors,such as optical sensors, can alternatively be employed to sense magneticfields from the medium. A thin hard coating 97 formed for example ofdiamond-like carbon (DLC), silicon carbide (SiC), tetrahedral amorphouscarbon (ta-C) or the like protects the MR sensor 90 from corrosion orother damage, the coating forming at least part of the medium-facingsurface 66. The MR sensor 90 is disposed adjacent to a substrate 61 onwhich the aforementioned thin film layers of the head 60 have beenformed. The substrate 61 may extend much further between the firstshield 92 and the leading end 62 than the distance between the firstshield and the trailing end 64, and may be formed of any appropriatesubstrate material known in the art of magnetic heads, such as alumina,silicon, alumina-titanium-carbide, ferrite, etc.

FIG. 2 is an expanded cross-sectional view that focuses on the regionaround pole tips 70 and 80, and FIG. 3 illustrates magnetic flux thatmay flow through those pole tips and into the medium 50 duringoperation. Magnetic flux, indicated by arrows 98, flows through softmagnetic pole layer 88 and is concentrated in high magnetic moment layer68. From layer 68 the flux 98 emanates from write pole tip 70 andtraverses media layer 58 to flow through the soft magnetic underlayer55, thereafter crossing return pole tip 80 to flow through layer 78.Flux from layer 68 also emanates from a trailing edge 96 of that layer,traversing gap 77 to flow into the return pole layer 80.

As shown in FIG. 2, the nonmagnetic gap 77 expands at a throat height69, which is measured from the medium-facing surface and in thisembodiment is essentially equal to the extension of ferromagneticpedestal 75 from the medium-facing surface 66. The throat height 69 is aparameter in controlling how much flux is diverted from layer 68 tolayer 78, rather than traveling through the medium, and thus affects theefficiency of the head. For most embodiments, a throat height 69 of lessthan about one micron is preferable. In this embodiment, nonmagnetic gap77 expands to be greater than one-half micron at a throat height of lessthan one-half micron. Pedestal 75 provides precise definition of thethroat height 69.

For clarity, trailing corner 71 of pole tip 70 is not labeled in FIG. 3due to the concentration of flux lines 98 at its location. Because thetrailing corner 71 is adjacent to both the soft magnetic underlayer 55and the soft magnetic pole layer 78, flux from that trailing corner mayflow into both underlayer 55 and pole layer 78, increasing the densityof flux emanating from the trailing corner 71. The highest concentrationof flux 98 traversing media layer 58 emanates from trailing corner 71and is directed at an angle that is neither perpendicular nor parallelto the medium-facing surface 66. The angled flux 98 provides increasedtorque to rotate magnetic dipoles in the media layer 58 that areoriented substantially perpendicular to the disk surface 53. In oneembodiment, the maximum flux density emanating from trailing corner 71is directed at an angle between twenty degrees and sixty degrees fromperpendicular to the medium surface 53, and preferably at aboutforty-five degrees to that surface 53.

Because the medium is moving relative to the head in the direction shownby arrow 59, a media layer 58 bit that has been magnetized by angledflux 98 from trailing corner 71 subsequently encounters flux that isdirected from soft underlayer 55 to pole tip 80. The flux 98 traversingmedia layer 58 adjacent to return pole tip 80, however, is much lessconcentrated than that adjacent to trailing corner 71, and also muchless effective due to being oriented substantially parallel to the easyaxis of magnetization of media layer 58.

FIG. 4 is a cutaway view of the head 60 of FIG. 1 as seen from themedium, looking through the thin transparent coating 97 of themedium-facing surface 66, which are therefore not evident in thisfigure. Although not necessarily drawn to scale, the dramaticallydifferent size of the write pole tip 70 compared to the return pole tip80 is apparent. The write pole tip 70 may be trapezoidal in shape, witha track-width dimension along trailing corner 71 of approximately 0.15micron or less, and a track-length dimension of approximately one-halfmicron or less, and preferably less than one-quarter micron. Themedium-facing area of write pole tip 70 is therefore less than 0.08square microns (less than 80,000 square nanometers). Return pole tip 80may measure on the order of 1.0 micron in the track-length dimension,and may extend 10 to 100 microns in the track-width dimension, largeenough that the full width of this embodiment is not shown in thiscutaway drawing. The medium-facing area of return pole tip 80 istherefore at least two orders of magnitude greater than that ofmedium-facing area of write pole tip 70.

FIG. 5 is a view of the head 60 as would be seen looking at the trailingend 64 and focusing on the active elements of the write transducer,including ferromagnetic layers 68, 78 and 88, and coil layer 91. Coilsections 82 are cutaway so that entire spiral coil layer 91 is notshown. Write pole tip 70 can be seen to have a much smaller track-widththan return pole tip 80. The ferromagnetic layers 68, 78 and 88 aremagnetically coupled in region 65.

FIG. 6 is a cutaway cross-sectional view of an electromagnetic head 160in which a write transducer 110 is disposed closer than an MR sensor 190to a wafer substrate 161. As with the previous embodiment, the head isin close proximity to a relatively moving medium 50.

The head 160 has a leading end 162, a trailing end 164 and amedium-facing surface 166. A first ferromagnetic layer 168, which maysometimes be called a write pole layer, is disposed in the head andterminates adjacent to the medium-facing surface in a first pole tip170, which may sometimes also be called a write pole tip. A secondferromagnetic layer 178, which may sometimes be called a return polelayer, is magnetically coupled to the first ferromagnetic layer 168 by asoft magnetic stud 112 in a region 165 that is removed from themedium-facing surface 166, the second ferromagnetic layer terminatingadjacent to the medium-facing surface in a second pole tip 180. Thesecond pole tip 180, which may sometimes be called a return pole tip, isdisposed between the first pole tip 170 and the trailing end 164. A softmagnetic pedestal 111 adjoins second ferromagnetic layer 178 to formpart of the second pole tip 180, the pedestal 111 being separated fromthe first pole tip by a nanoscale nonferromagnetic gap 177. A thirdferromagnetic layer 188 adjoins the first ferromagnetic layer 168 butterminates further from the medium-facing surface 166 than the firstpole tip 170. The ferromagnetic layers 111, 112, 168, 178 and 188 of thehead 160 may have a permeability of at least one thousand, while layer168 may also be formed of a high magnetic moment material, e.g., havinga magnetic saturation of at least twenty kiloGauss. First ferromagneticlayer 168 has a trailing edge 196 disposed adjacent to trailing end 164.A trailing corner 171 of first pole tip 170, disposed where first poletip 170 meets trailing edge 196, is approximately equidistant from softmagnetic underlayer 55 and soft magnetic pedestal 111.

A plurality of electrically conductive coil sections 182 are disposedbetween the first ferromagnetic layer 168 and the second ferromagneticlayer 178 to induce magnetic flux in the soft magnetic layers 111, 112,168, 178 and 188. Those ferromagnetic layers 111, 112, 168, 178 and 188form a magnetic loop around coil sections 182, the loop interrupted bynanoscale nonferromagnetic gap 177. Another plurality of electricallyconductive coil sections 186 are similarly disposed between the firstferromagnetic layer 168 and the leading end 162. Crosses 185 in the coilsections 182 indicate electric current that is flowing away from theviewer and into the page, while dots 186 in the coil sections 184indicate electric current that is flowing toward the viewer and out ofthe page. With electric current flowing in substantially oppositedirections in sections 182 and 184 as shown, the magnetic field from thecoil sections 182 and 184 adds together in the area between the sections182 and 184 and is at least partly cancelled in areas outside thesections 182 and 184 that are closer to the leading or trailing end.

The coil sections 182 in this embodiment are part of a first coil layer191 that spirals around coupling region 165 and includes electricallyconductive coil sections 195, and coil sections 184 are part of a secondcoil layer 193 that spirals around optional soft magnetic stud 179 andincludes electrically conductive coil sections 199. Coil sections 195have electric current that is flowing toward the viewer and out of thepage, as indicated by dots 186, while coil sections 199 have electriccurrent that is flowing away from the viewer and into of the page, asindicated by crosses 185. Advantages of this type of reversed doublecoil layer configuration include a stronger applied field between thecoil layers 191 and 193 and reduced or cancelled field leading andtrailing the coil layers, as well as reduced coil inductance and reducedamplification of stray signals due to an antenna effect. The coil layersmay spiral in identical directions, e.g., both spiraling inward in acounterclockwise direction when viewed from the trailing end, and beinterconnected at the center sections or outermost sections.Alternatively, the coil layers may spiral in opposite directions andhave the center section of one layer connected to the outermost sectionof the other layer.

Instead of the configuration shown in FIG. 6, coil sections 182 and 184may spiral in a barber pole formation around ferromagnetic layers 168and 188, without the need for coil sections 195 and 199. Alternatively,instead of plural coil sections 182, a single coil section, or multiplecoil sections, may pass between layers 168 and 178. For the case inwhich coil section 182 is a single section formed as a layer, that layermay be connected to a similar layer disposed between layer 188 and theleading end 162. This formation may be termed a single turn coil.

The ferromagnetic layers 111, 112, 168 and 178 of the head 160 togetherwith the soft magnetic underlayer 55 of the disk 50 form a magneticcircuit that traverses the media layer adjacent the first pole tip 170and the second pole tip 180. Although not clear in this cross-sectionalview, the second pole tip 80 has a medium-facing area that is at leasttwo orders of magnitude greater than that of the first pole tip 170, toavoid overwriting with the second pole tip signals that were imparted tothe media layer by the first pole tip.

The head 160 also includes a MR sensor 190 sandwiched between softmagnetic pole layer 178 and soft magnetic shield layer 194, with the MRsensor disposed within one-half micron of the return pole tip 180.Stated differently, the second pole layer is merged with the firstshield layer. An advantage of this configuration is that the coil layer193, which may have cured or hardbaked photoresist disposed between itscoils sections 184 and 199, is closer to the substrate, which can serveas a heat sink for resistive heat generated by the coil layer 193.Because cured or hardbaked photoresist has a greater coefficient ofthermal expansion than other materials of head 160, resistive heating ofthe coil layers may otherwise cause bulging of the coil layers thatcauses a slight protrusion at the medium-facing surface. In theembodiment shown, such protrusion would be reduced in coil layer 193 butoptionally not as greatly reduced in coil layer 191, which may result inslight protrusion of pole tips 170 and 180, which can help with writingsignals to the medium 50.

The MR sensor 190 can be any sensor that utilizes a change in resistancecaused by a change in magnetic field to sense that field, which may bemeasured as a change in current or voltage across the sensor, includinganisotropic magnetoresistive (AMR) sensors, spin-valve (SV) sensors,spin-tunneling (ST) sensors, giant magnetoresistive (GMR) sensors andcolossal magnetoresistive (CMR) sensors. A thin hard coating 197 formedfor example of DLC, SiC, ta-C or the like protects the MR sensor 190from corrosion or other damage, the coating forming at least part of themedium-facing surface 166. The substrate 161 may extend much furtherbetween the coil layer 193 and the leading end 162 than the distancebetween the coil layer 193 and the trailing end 164, and may be formedof any appropriate substrate material known in the art of magneticheads, such as alumina, silicon, alumina-titanium-carbide, etc.

FIG. 7 is a cutaway view of the head 160 of FIG. 6 as seen from themedium, looking through the thin transparent coating of themedium-facing surface, which are therefore not evident in this figure.Although not necessarily drawn to scale, the dramatically different sizeof the write pole tip 170 compared to the return pole tip 180 isapparent. The write pole tip 170 may be trapezoidal in shape, with atrack-width dimension along the trailing corner 171 of approximately0.15 micron (150 nanometers) or less, and a track-width dimension ofapproximately 0.25 micron (250 nanometers) or less. The medium-facingarea of write pole tip 170 is therefore less than 0.04 square microns(40,000 square nanometers). Return pole tip 180 may measure on the orderof 1.0 micron in the track-length dimension, and may extend 10 to 100microns in the track-width dimension, large enough that its full widthis not shown in this cutaway drawing. The medium-facing area of returnpole tip 180 is therefore at least two orders of magnitude greater thanthat of medium-facing area of write pole tip 170.

FIG. 8 shows a perspective view of a spiral coil layer 200 and a spiralcoil layer 202 that are interconnected at interconnect 205, toillustrate one kind of double reverse coil formation that may beemployed. Electrical connections 208 and 210 provide current for thecoil layers 200 and 202, provided by amplifiers and drive electronics. Atapered ferromagnetic write pole layer 212 and write pole tip 215 areshown but, for clarity, other pole layers, other pole tips and magneticcoupling regions are not shown.

Referring again to FIG. 1, a method for making the head 60 is described.The head 60 is formed in a number of thin-film transducer layers, alongwith thousands of similar heads, not shown, on the wafer substrate 61,which may be made of alumina-titanium-carbide, alumina, silicon-carbide,ferrite or other known materials. Atop the wafer substrate 61 the firstsoft magnetic shield layer 92 is formed, for example by window frameplating, either directly on the substrate or atop a seed layer, notshown. After completion of processing, first shield layer 92 may have athickness of about one or two microns, a height measured from themedium-facing surface of about thirty microns and a width of about tenor twenty microns, for example.

An alumina or other dielectric layer is then deposited and lapped toform a coplanar surface with the first shield layer 92. A firstnanoscale read gap layer of nonmagnetic, electrically insulatingmaterial is formed on the shield layer, followed by the magnetoresistive(MR) sensor 90. A second nanoscale read gap layer of nonmagnetic,electrically insulating material is then formed between the MR sensorand the second soft magnetic shield layer 94. The MR sensor 90 may beelectrically connected to the shield layers 92 and 94 in someembodiments, such as spin-dependent tunneling sensors.

The second shield layer 94 is formed, for example by window frameplating, to a thickness after lapping of about one or two microns and awidth of about ten or twenty microns, for example. The height of secondshield layer 94 is a controlled parameter in obtaining zero stray fieldat the MR sensor 90 for the dual reverse coil arrangement, and may beabout equal to that of the pole layers 68 and 88, or about ten micronsin this embodiment after completion of fabrication. Since other factorsmay be employed to obtain zero stray field at the MR sensor 90, theheight of the second shield layer may be in a range between about fivemicrons and one hundred microns.

After lapping the second shield layer 94 another dielectric layer isformed to a thickness that may preferably be between less than onemicron and several microns, upon which electrically conductive coillayer 93 is formed, for example by electroplating followed by curingphotoresist or filling with alumina. Coil layer 93 may be formed ofcopper, gold, silver or other electrically conductive materials. A coillayer 202 similar to coil layer 93 is shown in perspective view in FIG.8. Coil layer 93 is formed in a spiral pattern with winding sections 84substantially parallel to the medium-facing surface 66 in a regionadjacent to second shield 94. Coil layer 93 may have a thickness on theorder of one micron, and winding sections 84 may have a rectangularcross-section of about one micron in thickness by one and one-halfmicrons in height in one embodiment, with a distance between windingsections 84 of about one micron. The distance of the coil layer 93 fromthe media-facing surface 66 may be in a range between about two micronsand six microns in this embodiment.

After polishing the coil layer 93 a first portion of an electricallyconductive interconnect is formed, similar to interconnect 205 shown inFIG. 8, upon which another dielectric layer is formed to a thicknessthat may preferably be between less than one micron and several microns,after lapping that exposes the interconnect portion. The thirdferromagnetic layer 88 is then formed along with another portion of theelectrically conductive interconnect, for example by separate frameplating steps. The third soft magnetic layer 88 has a thickness afterlapping that may be about one micron, is spaced about one to threemicrons from the medium-facing surface, and extends about eight tofifteen microns from the medium-facing surface, for example. The thirdferromagnetic layer 88 has a tapered width that funnels magnetic flux tothe pole tip 70, the width ranging from about ten microns distal to themedia-facing surface 33 to lees than one micron, e.g., 0.2 micronadjacent to the pole tip 70.

The first ferromagnetic layer 68 is then formed of high magneticsaturation (high B_(SAT)) material, for example by sputtering or otherknown techniques. High magnetic saturation materials that may be used toform layer 68 include FeN and FeN based alloys, predominantly iron NiFe,CoFe and related alloys, etc. The first ferromagnetic layer 68 may havea tapered shape that mirrors that of third ferromagnetic layer 88 butextends further to terminate in pole tip 70. The first ferromagneticlayer 68 may be less than one-half micron in thickness and may be formedto have a trapezoidal cross-section parallel to the medium-facingsurface, as disclosed in U.S. patent application Ser. No. 09/933,508,which is incorporated by reference herein.

The nanoscale nonferromagnetic gap 77 is then formed of insulatingmaterial such as alumina, silicon dioxide or the like, or conductivematerial such as tantalum, chromium, nickel-chromium or the like, thethickness the gap 77 layer depending upon the desired spacing betweenthe pole tip 70 and the soft magnetic underlayer 55 of the medium 50 andthe desired angle of maximum flux from trailing corner 71. The softmagnetic pedestal 75 and soft magnetic stud 79 are then formed in plurallayers to a thickness of between about two and ten microns by techniquessuch as window frame plating to connect the pole layer 68 with the polelayer 78. After forming the gap 77 a first layer of soft magneticpedestal 75 and soft magnetic stud 79 are formed along with anotherportion of the electrically conductive interconnect, for example byseparate frame plating steps.

Electrically conductive coil layer 91 may then be formed, for example byframe plating of copper, gold, silver or other electrically conductivematerials. Coil layer 91, similar to coil layer 200 shown in FIG. 8, isformed in a spiral pattern with coil sections 82 that are substantiallyparallel to the media-facing surface 33 in a region adjacent to polelayer 68. A central coil section 82 is connected with the electricallyconductive interconnect. Coil layer 91 may have a thickness on the orderof one micron, and winding sections 84 may have a rectangularcross-section of about one micron in thickness by one and one-halfmicrons in height in one embodiment, with a distance between windingsections 84 of about one micron.

After polishing the coil layer 91 a final portion of soft magneticpedestal 75 and soft magnetic stud 79 are formed, upon which anotherdielectric layer is formed to a thickness that may preferably be betweenless than one micron and several microns, after lapping that exposes thestud portion. The remainder of second ferromagnetic layer 78 is thenformed, for example by frame plating, to a thickness between less thanone micron and several microns, e.g., 1.5 microns, a height thatpreferably matches that of the ferromagnetic layer 68 and a width thatmay be tens of microns in the coupling region 65. Ferromagnetic layer 78terminates adjacent the media-facing surface in a second pole tip 80that faces the medium 50, second pole tip 80 having a medium-facingsurface at least two orders of magnitude larger than that of first poletip 70. For example, second pole tip 80 may have a media-facing areathat is greater than 10 square microns, so that second pole tip may havea medium-facing area that is between 100 and 100,000 times larger thanthat of first pole tip 70.

A protective coating of dielectric material such as alumina or DLC isthen formed over ferromagnetic layer 78, to form the trailing end of thehead 60. Electrical connections, similar to elements 208 and 210 shownin FIG. 8, extend from coil layers 91 and 93, respectively, to provideelectrical contacts either on the trailing end 64 or on a back surfaceof the head disposed opposite to the media-facing surface 66. Similarelectrical leads, not shown, extend from the MR sensor 90 to provideadditional electrical contacts either on the trailing end 64 or the backsurface.

After forming the protective coating to create the trailing end 64, thewafer substrate 61 and attached thin film layers are diced to form rowsof heads, as is known in the art, and the medium-facing surface isformed. The protective coating 97 of hard dielectric material such asDLC, ta-C, SiC or the like is formed. The rows are then divided intoindividual heads that are attached to suspensions for positioningadjacent to disks in drive systems.

1. A magnetic head for writing information on a relatively-movingmedium, the head comprising: a body having a leading end, a trailing endand a medium-facing surface, the body including an electricallyconductive coil section at least partly encircled by a magnetic loopterminating in a write pole tip and a return pole tip that are disposedadjacent to the medium-facing surface and separated from each other by ananoscale nonmagnetic gap, wherein the return pole tip is disposedbetween the write pole tip and the trailing end and the return pole tiphas a medium-facing area that is at least two orders of magnitudegreater than that of the write pole tip.
 2. The head of claim 1, whereinthe write pole tip has a trialing corner disposed closest to thetrailing end, and magnetic flux emanating from the write pole tip has amaximum density emanating from the trailing corner and directed at anangle that is not perpendicular to the write pole tip.
 3. The head ofclaim 1, further comprising a magnetoresistive sensor disposed less thanone-half micron from the return pole tip.
 4. The head of claim 1,further comprising an electrically conductive winding sectionelectrically connected to the coil section, such that a current flowingin a first direction in the coil section flows in a substantiallyopposite direction in the winding section, with the coil sectiondisposed between the write pole tip and the trailing end, and thewinding section disposed between the write pole tip and the leading end.5. The head of claim 4, wherein the coil section is part of anelectrically conductive coil that spirals around a first magneticsection that magnetically couples the write pole tip to the return poletip, and the winding section is part of an electrically conductivewinding that spirals exterior to the magnetic loop, such that a currentspiraling in a first direction in the coil spirals in a substantiallyopposite direction in the winding.
 6. The head of claim 1, wherein thecoil section is part of an electrically conductive coil that spiralsaround a first magnetic section that magnetically couples the write poletip to the return pole tip, and the coil is connected to an electricallyconductive winding that spirals exterior to the magnetic loop, such thata current flowing in a first direction in the coil flows in asubstantially opposite direction in the winding.
 7. The head of claim 1,wherein the write pole tip has a medium-facing area that is less thanabout thirty thousand square nanometers.
 8. The head of claim 1, whereinthe write pole tip has a trailing corner adjoining the nonmagnetic gap,and magnetic flux emanating from the trailing corner has a maximumdensity at an angle that is between about twenty degrees and sixtydegrees from perpendicular to the medium-facing surface.
 9. The head ofclaim 1, wherein the write pole tip has a trailing corner adjoining thenonmagnetic gap, the return pole tip has a leading corner adjoining thenonmagnetic gap, and the trailing corner is made of higher magneticsaturation material than that of the leading corner.
 10. The head ofclaim 1, wherein the nonmagnetic gap expands at a throat height, thethroat height being measured from the medium-facing surface and beingless than one-half micron.
 11. The head of claim 1, further comprising amagnetoresistive sensor that is disposed in the body between a pair ofshields that are located adjacent to the magnetic loop.
 12. The head ofclaim 1, further comprising a magnetoresistive sensor disposed less thanone-half micron from the return pole tip.
 13. The head of claim 1wherein the write pole tip has a trialing corner disposed closest to thetrailing end, and magnetic flux emanating from the write pole tip has amaximum density emanating from the trailing corner and is directed at anangle that is not perpendicular to the write pole tip and is toward thereturn pole tip.
 14. A magnetic head for writing information on arelatively-moving medium containing a media layer and a soft magneticunderlayer, the head comprising: a body having a leading end, a trailingend and a medium-facing surface, the body including an electricallyconductive coil section at least partly encircled by a magnetic loopterminating in a write pole tip and a return pole tip that are disposedadjacent to the medium-facing surface and separated from each other by ananoscale nonmagnetic gap, wherein the return pole tip is disposedbetween the write pole tip and the trailing end and the return pole tiphas a medium-facing area that is at least two orders of magnitudegreater than that of the write pole tip.
 15. The head of claim 14,further comprising a magnetoresistive sensor disposed less than one-halfmicron from the return pole tip.
 16. The head of claim 14, furthercomprising an electrically conductive winding section electricallyconnected to the coil section, such that a current flowing in a firstdirection in the coil section flows in a substantially oppositedirection in the winding section, with the coil section disposed betweenthe write pole tip and the trailing end, and the winding sectiondisposed between the write pole tip and the leading end.
 17. The head ofclaim 14, wherein a distance between the write pole tip and the returnpole tip is approximately equal to a spacing between the write pole tipand the soft magnetic underlayer of the medium.
 18. The head of claim14, wherein the coil section is part of an electrically conductive coilthat spirals around a first magnetic section that magnetically couplesthe write pole tip to the return pole tip, and the coil is connected toan electrically conductive winding that spirals exterior to the magneticloop, such that a current spiraling in a first direction in the coilspirals in a substantially opposite direction in the winding.
 19. Thehead of claim 14, wherein the write pole tip has a medium-facing areathat is less than about thirty thousand square nanometers.
 20. The headof claim 14, wherein the write pole tip has a trailing corner disposedadjacent to the trailing end, and magnetic flux from the trailing cornerthat impinges the media layer is directed in a range between abouttwenty degrees and sixty degrees from perpendicular to the medium-facingsurface.
 21. The head of claim 14, wherein the magnetic loop includes afirst ferromagnetic layer and a second ferromagnetic layer, the firstferromagnetic layer including the write pole tip and the secondferromagnetic layer including the return pole tip, the secondferromagnetic layer is separated from the first ferromagnetic layer bymore than one-half micron at a throat height, the throat height beingmeasured from the medium-facing surface and being less than one-halfmicron.
 22. The head of claim 14, wherein the nonmagnetic gap expands ata throat height, the throat height being measured from the medium-facingsurface and being less than one-half micron.
 23. The head of claim 14,wherein the write pole tip has a trialing corner disposed closest to thetrailing end, and magnetic flux emanating from the write pole tip has amaximum density emanating from the trailing corner and directed at anangle that is not perpendicular to the write pole tip.
 24. The head ofclaim 14 wherein the write pole tip has a trialing corner disposedclosest to the trailing end, and magnetic flux emanating from the writepole tip has a maximum density emanating from the trailing corner and isdirected at an angle that is not perpendicular to the write pole tip andis toward the return pole tip.
 25. A magnetic head for writinginformation on a relatively-moving medium containing a media layer and asoft magnetic underlayer, the head having a leading end, a trailing end,and a medium-facing surface, the head comprising: a first ferromagneticlayer terminating in a first pole tip disposed adjacent to themedium-facing surface, a second ferromagnetic layer magnetically coupledto the first ferromagnetic layer in a region that is removed from themedium-facing surface, the second ferromagnetic layer terminating in asecond pole tip that is disposed adjacent to the medium facing surfaceand located between the first pole tip and the trailing end, the secondpole tip being separated from the first pole tip by a nanoscalenonferromagnetic gap and having a medium-facing aria that is at leasttwo orders of magnitude greater than that of the first pole tip; and anelectrically conductive coil section disposed between the firstferromagnetic layer and the second ferromagnetic layer to inducemagnetic flux in the first ferromagnetic layer.
 26. The head of claim25, further comprising an electrically conductive winding sectionelectrically connected to the coil section, with the first ferromagneticlayer disposed between the coil section and the winding section, suchthat a current spiraling in a first direction in the coil section flowsin a substantially opposite direction in the winding section.
 27. Thehead of claim 25, wherein the coil section is part of an electricallyconductive coil that spirals around the region that magnetically couplesthe first ferromagnetic layer to the second ferromagnetic layer, and thecoil is connected to an electrically conductive winding that spiralsaround an axis that is aligned with the region, such that a currentspiraling in a first direction in the coil spirals in a substantiallyopposite direction in the winding.
 28. The head of claim 25, wherein thefirst pole tip has a medium-facing area that is less than about thirtythousand square nanometers.
 29. The head of claim 25, wherein the firstpole tip has a trailing corner disposed adjacent to the trailing end,and magnetic flux from the trailing corner that impinges the media layeris directed in a range between about twenty degrees and sixty degreesfrom perpendicular to the medium-facing surface.
 30. The head of claim25, wherein the nonferromagnetic gap expands at a throat height, thethroat height being measured from the medium-facing surface and beingless than one micron.
 31. The head of claim 25, further comprising amagnetoresistive sensor disposed less than one-half micron from thesecond pole tip.
 32. The head of claim 25, wherein a distance betweenthe first pole tip and the second pole tip is approximately equal to aspacing between the first pole tip and the soft magnetic underlayer ofthe medium.
 33. The head of claim 25 wherein the first pole tip has atrialing corner disposed closest to the trailing end, and magnetic fluxemanating from the first pole tip has a maximum density emanating fromthe trailing corner and is directed at an angle that is notperpendicular to the first pole tip and is toward the second pole tip.34. A magnetic head for writing information on a relatively-movingmedium, the head having a leading end, a trailing end, and amedium-facing surface, the head comprising: a first ferromagnetic writepole layer terminating in a write pole tip disposed adjacent to themedium-facing surface, a ferromagnetic return pole structure disposedbetween the write pole layer and the trailing end and magneticallycoupled to the write pole layer in a coupling region, the return polestructure terminating adjacent to the medium-facing surface in a returnpole tip having an area that is at least two orders of magnitude greaterthan that of the write pole tip, the pole tips separated by a nanoscalenonferromagnetic gap and; a first electrically conductive coil sectionthat winds about the coupling region, the first coil including at leastone coil section that is disposed between the write pole layer and thereturn pole structure; a second electrically conductive coil thatcarries current in a substantially opposite direction to that flowing inthe first coil to induce a magnetic field between the coils that isstronger than the field induced outside the coils, the second coildisposed closer than the first coil to the trailing end.
 35. The head ofclaim 34, wherein the first ferromagnetic write pole layer has athickness that is less than one-half micron.
 36. The head of claim 34,further comprising a magnetoresistive sensor disposed within one-quartermicron from the return pole tip.
 37. The head of claim 34, wherein thesecond ferromagnetic layer is separated from the first ferromagneticlayer by more than one-half micron at a throat height, wherein thethroat height is measured from the medium-facing surface and is lessthan one-half micron.